The present invention is directed to an improved differential sense amplifier; differential amplifiers are widely used in memory sensing circuitry accessing. In particular, the present invention is directed to a differential sense amplifier having improved sensitivity.
One example of the use of differential amplifiers for memory sensing circuitry is in flash programmable read only memories (PROM). In such flash PROMs, a dummy reference bit line is generally used as one of a pair of differential inputs to a differential sense amplifier. The other of the pair of inputs is the input to be measured for changes with respect to the dummy reference bit line. It is important that there be a definitive distinction between the paired inputs in each of two states of the monitored memory, or bit, cell. There usually is an indication of a logical "1" in one cell state, such as when the cell is charged or contains data; and a logical "0" in another cell state, such as when the cell is not charged or contains no data. The sensitivity of the sense amplifier is a key consideration in determining the respective states of bit cells in a memory array.